But ask yourself. Is this that easy? Is this the "the best beats the rest!" kind of game?

Basics. The sensors the Swedish navy are using to detect activities are old style stuff dug up from the graveyard of Swedish naval intel tech suppliers and none of them have been at the forefront since, ever.
So the noice and biasis from the sensors are not good to say the least.
The intel from the previous generation of sensors gave "clear indication" on sub maritime vehicles back in the 90-ies when they couldn't differ from krill shoals. And simpler.
Today?
That's what being tested right now. How good sensors are in Swedish naval intel is pretty much the standard of what is around the Baltics. Maybe even top of the line in this wet region.
So why not compromise it with the least available efforts (resources) and measure the temperature of the response by type of channel and response time?
I'd do the same.